De-bone the lamb shanks, make 4 loins from the meat, salt and close in plastic wrap, making a round shape.
Leave in the refrigerator for 24 hours.
Vacuum pack and cook them at 65°C for 2 hours.
Remove from the Roner and brown in a pan with butter, garlic and thyme.
Let it rest while maintaining it at 50°C.
Lemony Potato Purée
Cook the potatoes in water, peel and then pass through a mill.
Stir them in a baking dish with milk, softened butter and lemon juice.
Adjust salt and pepper and keep stirring until the desired consistency is reached.
Preparing the plate
On a plate, spread the purée into a straight line.
Cut a slice of lamb and place in the centre, dressing with some of the roasting sauce.